1. Field of the Invention
The present invention relates to a vibrator, a vibration gyro including a vibrator, and an electronic device including a vibration gyro. More particularly, the present invention relates to a vibrator for use in, for example, a vibration gyro which is used in a hand-shake correction device for a video camera, a navigation system or other suitable apparatus, a vibration gyro including the above-described vibrator, and an electronic device including the above-described vibration gyro.
2. Description of the Related Art
As examples of vibrators for a vibration gyro, a vibrator disclosed in Japanese Unexamined Patent Application Publication No. 7-151552 (hereinafter referred to as a first related example), and a vibrator disclosed in Japanese Unexamined Patent Application Publication No. 7-332988 (hereinafter referred to as a second related example) are known.
In the first related example, interdigital electrodes are formed by arranging comb electrodes opposite to each other on the surface of a columnar vibrating member constituted of a piezoelectric body, and polarization processing is performed for the piezoelectric body between the comb electrodes by applying a voltage between the comb electrodes. Furthermore, the vibrating member is caused to be vibrated by applying a voltage between the polarized comb electrodes, and the Coriolis force is detected.
In the second related example, a vibrator is formed by bonding together two piezoelectric substrates, which are polarized in mutually opposite directions, and the vibrator is caused to be vibrated by applying an AC voltage between the electrodes formed on the two surfaces of the vibrator, and the Coriolis force is detected.
However, in the first related example, since it is necessary to form interdigital electrodes on a curved surface, a problem arises in that the formation of the electrodes requires much labor and time, resulting in an increase in the cost. In addition, since the taking-out of leads from the interdigital electrodes becomes three-dimensional, another problem occurs in that the installation of the leads also requires much labor and time, and that the leads might hinder vibration.
In the second related example, it is necessary to bond together the two piezoelectric substrates, and therefore, if appropriate bonding conditions are not satisfied, environmental temperature, moisture, secular changes and other undesired effects might vary the bonding state of the bonded layer. In this case, a problem arises in that the vibration condition of the vibrator varies, resulting in variations in the detection accuracy of the Coriolis force. Additionally, it is necessary to provide support members on both surfaces of the vibrator since the support members each double as a lead. This raises another problem of increased cost due to an increase in assembly man-hours.
In order to overcome the problems described above, preferred embodiments of the present invention provide a vibrator which is constructed so as to allow its electrodes to be easily formed and requiring a smaller number of assembly man-hours, and also provide a vibration gyro including such a novel vibrator, and an electronic device including such a novel vibration gyro.
According to a preferred embodiment of the present invention, a vibrator includes a vibrating member defined by a piezoelectric body, a drive electrode disposed on the surface of the vibrating member and extending along a length direction of the vibrating member, and two detection electrodes each disposed adjacent to the drive electrode. In this vibrator, the drive electrode and each of the detection electrodes have an interdigital electrode portion defined by mutually opposed comb electrodes which are arranged such that the direction in which the teeth thereof extend is substantially perpendicular to the length direction of the vibrating member.
Preferably, the above-described vibrating member is polarized between the drive electrode and each of the detection electrodes. Alternatively, it is preferable that the above-described vibrating member be polarized in the length direction thereof, and that, in the interdigital electrode portion, the drive electrode be arranged so as to deviate in the length direction of the vibrating member with respect to each of the detection electrodes.
Furthermore, it is preferable that the above-described vibrating member have a planar portion extending along the length direction thereof, and that the drive electrode and the detection electrodes be disposed on the planar portion.
According to another preferred embodiment of the present invention, a vibrator includes a vibrating member defined by a piezoelectric body, a drive electrode disposed on the surface of the vibrating member along a length direction of the vibrating member, a reference electrode disposed adjacent to the drive electrode, and two detection electrodes each disposed adjacent to the reference electrode. In this vibrator, the drive electrode and the reference electrode, and the reference electrode and each of the detection electrodes, have an interdigital electrode portion defined by mutually opposed comb electrodes which are arranged such that the direction in which the teeth thereof extend is substantially perpendicular to the length direction of the vibrating member. Also, the vibrating member is preferably polarized between the drive electrode and the reference electrode, and between the reference electrode and each of the detection electrodes. The vibrating member preferably has a planar portion along the length direction thereof, and the drive electrode, the reference electrode, and the detection electrodes are disposed on the planar portion.
According to another preferred embodiment of the present invention, a vibrator includes a vibrating member defined by a piezoelectric body, a drive electrode disposed on the surface of the vibrating member along a length direction of the vibrating member, a reference electrode disposed adjacent to the drive electrode, and two detection electrodes each disposed adjacent to the reference electrode. In this vibrator, the drive electrode and the reference electrode, and the reference electrode and each of the detection electrodes, preferably have an interdigital electrode portion defined by mutually opposed comb electrodes which are arranged such that the direction in which the teeth thereof extend is substantially perpendicular to the length direction of the vibrating member. Also, the vibrating member is preferably polarized in the length direction thereof, and in the interdigital electrode portion, the drive electrode and each of the detection electrodes are arranged so as to deviate in the length direction of the vibrating member with respect to the reference electrode.
It is preferable that the above-described vibrating member have a planar portion extending along the length direction thereof, and that the drive electrode, the reference electrode, and the detection electrodes be disposed on the planar portion.
In the vibrator according to preferred embodiments of the present invention, it is preferable that support members are fixed to the planar portion, in the vicinity of the vibration nodes of the above-described vibrating member.
Furthermore, another preferred embodiment of the present invention provides a vibration gyro including the novel vibrator according to the various preferred embodiments described above.
Moreover, a further preferred embodiment of the present invention provides an electronic device including the novel gyro according to the preferred embodiment described in the preceding paragraph.
With these arrangements, the vibrator according to various preferred embodiments of the present invention enables a significant reduction in the cost and stabilization of performance.
The vibration gyro according to a preferred embodiment of the present invention allows a significant reduction in the cost and an improvement in the performance.
The electronic device according to another preferred embodiment of the present invention also allows a reduction in the cost and an improvement in the performance.
The above and other elements, characteristics, features, and advantages of the present invention will become clear from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings.